Device for measuring two physical quantities

ABSTRACT

A device for measuring at least one physical quantity includes a direct voltage source and a measuring sensor coupled to the voltage source, which sensor is configured to measure a physical quantity. A current regulator is connected between the direct voltage source and the measuring sensor, and a voltmeter is connected in parallel with the measuring sensor so that a voltage detected by the voltmeter is indicative of the measured quantity.

CROSS-REFERENCE

This application claims priority to German patent application no. 102020 202 224.0 filed on Feb. 20, 2020, the contents of which are fullyincorporated herein by reference.

TECHNOLOGICAL FIELD

The present disclosure is directed to devices for measuring physicalquantities and to electronic components of such devices.

BACKGROUND

A sensor is a device that transforms the state of an observed physicalquantity into a usable one, such as an electrical voltage or current.

One examiner of a sensor is an accelerometer, which, when attached to amoving object, can measure the linear acceleration of that object.

Piezoelectric accelerometers, for example, have the property of becomingelectrically charged when subjected to deformation.

As the piezoelectric phenomenon works in both directions, accelerometersalso deform when they are electrically charged which allows anelectrical voltage proportional to the acceleration to be collected.

Today, such an accelerometer may have dimensions of only a fewmillimeters or even less, so that it can be integrated directly on anelectronic card or circuit board or even in the chip of a computer andthus not take up a significant amount of space or require specificconnectors.

Other types of sensors such as a resistance temperature detectors arealso known. These sensors can be configured to measure a temperatureusually using a typical resistance value of 1000 ohm at 0° C.

The current flowing through the resistor generates a voltage to bemeasured to determine the temperature. It is based on the fact that theelectrical resistance of platinum varies with temperature.

In contrast to the accelerometer, which is usually supplied with aconstant current with a wide typical tolerance of ±20%, the resistancetemperature detector must be supplied with a constant, direct currentwith an accuracy tolerance of typical 0.2% or less in order to deliveraccurate temperature values.

In order to supply an accelerometer and a resistance temperature sensor,a solution was to add components to the circuit such as switches inorder to select the sensor to be supplied, according to the deliveredcurrent.

This solution also requires an addition of programmed modules to controlthese components and thus the selection between the accelerometer andthe resistance temperature detector.

The measuring device is then cluttered with complex circuitry in orderto carry out the measures.

SUMMARY

One aspect of the present disclosure is to measure at least one physicalquantity such as temperature or acceleration without cluttering up themeasuring device.

For this purpose, a first aspect of the disclosure comprises a methodfor measuring at least one physical quantity comprising a supply of atleast one measuring sensor configured to measure a physical quantity, bya direct voltage and a current regulation configured to supply thesensor with a constant direct current.

Thanks to the invention, it is now possible to replace one measuringsensor by another one without adding components.

As a matter of fact, each sensor can deliver accurate values when it'spowered by the constant direct current.

Thus, there is no need to add electronics to select the sensor to power.

In one embodiment, the regulated current has a precision tolerance ofless than or equal to 0.2%.

By this way, any sensor may be implemented without cluttering up thecircuit with switches for example.

In one embodiment, the physical quantity is a temperature or anacceleration.

According to another aspect, the invention further comprises a devicefor measuring at least one physical quantity, comprising at least onedirect voltage source generator, at least one measuring sensor coupledto said voltage source generator, configured to measure a physicalquantity, and a regulator coupled to the sensor and configured togenerate a constant direct current.

In one embodiment, the current regulator has a precision tolerance ofless than or equal to 0.2%.

In one embodiment, the physical quantity is a temperature or anacceleration.

According to an embodiment, the temperature sensor is a resistancetemperature detector.

Another aspect of the disclosure comprises a method that includesproviding a sensor configured to sense a physical condition, connectinga direct voltage source to the sensor, connecting a current regulatorbetween the direct voltage source and the sensor, and connecting avoltmeter in parallel with the sensor to determine a voltage indicativeof the physical condition sensed by the sensor.

A further aspect of the disclosure comprises a device for measuring atleast one physical quantity that includes a direct voltage source and ameasuring sensor coupled to the voltage source, the measuring sensorbeing configured to measure a physical quantity. The device alsoincludes a current regulator connected between the direct voltage sourceand the measuring sensor and a voltmeter connected in parallel with themeasuring sensor. A voltage detected by the voltmeter is indicative ofthe measured quantity.

Another aspect of the disclosure comprises a circuit that includes a DCvoltage source having an input and an output, the voltage source beingconfigured to produce a voltage output signal from the output. Thecircuit also includes a current regulator having an input and an output,the current regulator input being configured to receive the voltageoutput signal and the current regulator being configured to produce acurrent output signal from the current regulator output. The circuitalso includes a sensor having a first connection and a secondconnection, the first connection being configured to receive the currentoutput signal from the current regulator, an d the second connectionbeing connected to the input of the DC voltage source. A voltmeter isconnected to the first connection and the second connection and isconfigured to detect a voltage across the sensor, where the detectedvoltage is indicative of an acceleration when the sensor is anaccelerometer and the detected voltage is indicative of a temperaturewhen the sensor is a resistance temperature detector.

The invention further comprises an integrated circuit comprising ameasuring device as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention and its advantages will be better understood bystudying the detailed description of a specific embodiment given by wayof a non-limiting example and illustrated by the appended drawings inwhich:

FIGS. 1A and 1B illustrate a conventional measuring device.

FIGS. 2A and 2B schematically illustrate a measuring device according toa first and a second embodiment of the invention.

FIG. 3 is a schematic representation of a current regulator of themeasuring device of FIG. 2.

DETAILED DESCRIPTION

FIGS. 1A and 1B show a measuring device 1 configured to measure twophysical quantities such as temperature and acceleration.

In order to collect temperature data, the measuring device 1 of FIG. 1Bincludes a resistance temperature detector RTD with a typical resistanceof 1000 ohm at 0° C. that is suitable for receiving a current with aprecision tolerance of less than or equal to 0.2% to deliver accuratetemperature values.

Of course, the resistance temperature detector may be replaced by anytemperature sensor with the same tolerance interval.

To measure the acceleration, the measuring device 1 of FIG. 1A includesan accelerometer AC of conventional structure which may be supplied witha constant current with a wide tolerance of ±20%.

The resistance temperature detector RTD and the accelerometer AC arepowered by a direct voltage source generator SC such as a battery, whichdelivers an electrical voltage VIN.

The generator SC is coupled to a current regulator PCS configured todeliver a constant direct current Io and to a non-precision currentgenerator NPCS configured to deliver a non-constant direct current I₁₀.

In particular, the current regulator PCS is coupled to the resistancetemperature detector RTD and the non-constant direct current NPCS iscoupled to the accelerometer AC.

As the current regulator PCS has a precision tolerance of 0.2% in thisexample, it allows the resistance temperature detector RTD to beoperational.

The connections are here established by two switches SW1 and SW2 whereinswitch SW1 is configured to enable or disable the flow of current I₁₀from the non-constant direct current NPCS to power the accelerometer AC.

Similarly, switch SW2 is configured to enable or disable the flow ofcurrent I₀ from the current regulator PCS to power the resistancetemperature detector RTD.

As switches SW1 and SW2 are configured to select the sensor to besupplied according to the delivered current, this embodiment requires anaddition of programmed modules to control switches SW1, SW2 and thus theselection between the accelerometer AC and the resistance temperaturedetector RTD.

In order to overcome the use of these components, FIGS. 2A and 2Billustrate only one current regulator PCS which can be coupled to theaccelerometer AC or to the resistance temperature detector RTD.

To read the acceleration, the accelerometer AC is coupled in parallel,at nodes C and D, to a first voltmeter V1 configured to measure avoltage U_(CD) at its terminals as shown in FIG. 2A.

As for the acceleration reading, the resistance temperature detector iscoupled in parallel, at nodes E and F, to a second voltmeter V2configured to measure a voltage U_(EF) at its terminals as illustratedin FIG. 2B.

FIG. 3 shows a schematic representation of the PCS current controllerwith conventional circuitry that may be used in the measuring device.Alternatively, other types of PCS current controller may be used.

The current regulator PCS includes here an electronic amplifier OP whichreceives as an input the voltage V_(IN), delivered by the sourcegenerator SC.

The amplifier OP is configured to output a control voltage to drive afield effect transistor T_(R1) which is coupled to a bipolar transistorT_(R2).

The transistor T_(R1) is here configured to drive the bipolar transistorin order to output the regulated current I₀ that will power theaccelerometer AC and the resistance temperature detector RTD.

Furthermore, it should be noted that the gain of the amplifier OPdepends on the parameters of the transistors T_(R1), R_(R2) and theresistors R1 and R2.

The invention is not limited to these embodiments but comprises all thevariants. For example, other components may be connected between theaccelerometer AC or the resistance temperature detector RTD as long asthey do not influence the accuracy of the regulated current I₀.

Representative, non-limiting examples of the present invention weredescribed above in detail with reference to the attached drawings. Thisdetailed description is merely intended to teach a person of skill inthe art further details for practicing preferred aspects of the presentteachings and is not intended to limit the scope of the invention.Furthermore, each of the additional features and teachings disclosedabove may be utilized separately or in conjunction with other featuresand teachings to provide improved devices for measuring two physicalquantities.

Moreover, combinations of features and steps disclosed in the abovedetailed description may not be necessary to practice the invention inthe broadest sense, and are instead taught merely to particularlydescribe representative examples of the invention. Furthermore, variousfeatures of the above-described representative examples, as well as thevarious independent and dependent claims below, may be combined in waysthat are not specifically and explicitly enumerated in order to provideadditional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intendedto be disclosed separately and independently from each other for thepurpose of original written disclosure, as well as for the purpose ofrestricting the claimed subject matter, independent of the compositionsof the features in the embodiments and/or the claims. In addition, allvalue ranges or indications of groups of entities are intended todisclose every possible intermediate value or intermediate entity forthe purpose of original written disclosure, as well as for the purposeof restricting the claimed subject matter.

What is claimed is:
 1. A method comprising: providing a sensorconfigured to sense a physical condition, connecting a direct voltagesource to the sensor, connecting a current regulator between the directvoltage source and the sensor, and connecting a voltmeter in parallelwith the sensor to determine a voltage indicative of the physicalcondition sensed by the sensor.
 2. The method according to claim 1,wherein the voltage is indicative of an acceleration when the sensorcomprises an accelerometer and the voltage is indicative of atemperature when the sensor comprises a resistance temperature detector.3. The method according to claim 2, wherein the current regulator has aprecision tolerance of less than or equal to 0.2%.
 4. The methodaccording to claim 1, wherein the current regulator has a precisiontolerance of less than or equal to 0.2%.
 5. The method according toclaim 4, wherein the physical quantity is a temperature or anacceleration.
 6. A device for measuring at least one physical quantity,comprising: a direct voltage source, a measuring sensor coupled to thevoltage source, the measuring sensor being configured to measure aphysical quantity, a current regulator connected between the directvoltage source and the measuring sensor, and a voltmeter connected inparallel with the measuring sensor, wherein a voltage detected by thevoltmeter is indicative of the measured quantity.
 7. The deviceaccording to claim 6, wherein the voltage is indicative of anacceleration when the measuring sensor comprises an accelerometer andthe voltage is indicative of a temperature when the measuring sensorcomprises a resistance temperature detector.
 8. The device according toclaim 7, wherein the current regulator has a precision tolerance of lessthan or equal to 0.2%.
 9. The device according to claim 6, wherein thecurrent regulator has a precision tolerance of less than or equal to0.2%.
 10. The device according to claim 9, wherein the physical quantityis a temperature or an acceleration.
 11. An integrated circuitcomprising a measuring device according to claim
 6. 12. A circuitcomprising: a DC voltage source having an input and an output, thevoltage source being configured to produce a voltage output signal fromthe output, a current regulator having an input and an output, thecurrent regulator input being configured to receive the voltage outputsignal and the current regulator being configured to produce a currentoutput signal from the current regulator output, a sensor having a firstconnection and a second connection, the first connection beingconfigured to receive the current output signal from the currentregulator, and the second connection being connected to the input of theDC voltage source, a voltmeter connected to the first connection and thesecond connection and configured to detect a voltage across the sensor,wherein the detected voltage is indicative of an acceleration when thesensor is an accelerometer and the detected voltage is indicative of atemperature when the sensor is a resistance temperature detector.